As the resolution of a liquid crystal display panel is becoming higher and higher, PPI (Pixels per inch) also gets higher and higher. Narrow bezel is required for a liquid crystal display panel of high PPI, therefore, all current liquid crystal display panels of high PPI adopt the LTPS (Low Temperature Poly-silicon) technology. How to realize the narrow bezel of liquid crystal display panels of high PPI adopting a-Si technology is a problem currently to be solved urgently.